Perceptual learning is known to improve amblyopic vision in older children and adults. The present study investigated the effect of perceptual learning on amblyopic vision in children aged 8-16 and its relationship with previous patching treatment. Children were divided into two groups. The patching group consisted of 10 children who had previously been treated with the patching method for >18 months. The non-patching group consisted of 14 children who had not been treated with eye-patching. During training the children identified whether a full-contrast square-wave grating was tilted 45o or 135o from vertical in a staircase procedure that estimated the cutoff spatial frequency over 60 one-hour daily sessions (over 14,000 trials). After training the grating acuity improved greatly in all non-patching group children, many having grating acuity improved to near 30 cpd. Grating acuity was not significantly improved in most patching group children who had better grating acuity to start with. Meantime, E-acuity was improved more or less in both groups, with the magnitude varying from child to child. Some children in the patching group had improved E-acuity near 20/20 or better, but none in the non-patching group had improved E-acuity close to normal. Stereo acuity was also improved in some children in both groups. Currently a number of children from two groups are doing E-acuity training and the results will be reported as part of the abstract. Our preliminary results indicate that training induced grating acuity improvement is mainly shown in non-patching group, and this improvement is not directly related to letter acuity improvement, probably as a result of different mechanism underlying grating acuity and letter identification, which is inconsistent to previous reports. Moreover, perceptual training alone may not be a sufficient treatment for older amblyopic children. Rather it works best for children with previous patching history.